1. Field of the Invention
The present invention relates to a thermally-assisted magnetic recording head for use in thermally-assisted magnetic recording where a recording medium is irradiated with near-field light to lower the coercivity of the recording medium for data writing.
2. Description of the Related Art
Recently, magnetic recording devices such as magnetic disk drives have been improved in recording density, and thin-film magnetic heads and recording media of improved performance have been demanded accordingly. Among the thin-film magnetic heads, a composite thin-film magnetic head has been used widely. The composite thin-film magnetic head has such a structure that a read head section including a magnetoresistive element (hereinafter, also referred to as MR element) for reading and a write head section including an induction-type electromagnetic transducer for writing are stacked on a substrate. In a magnetic disk drive, the thin-film magnetic head is mounted on a slider that flies slightly above the surface of the recording medium.
To increase the recording density of a magnetic recording device, it is effective to make the magnetic fine particles of the recording medium smaller. Making the magnetic fine particles smaller, however, causes the problem that the magnetic fine particles drop in the thermal stability of magnetization. To solve this problem, it is effective to increase the anisotropic energy of the magnetic fine particles. However, increasing the anisotropic energy of the magnetic fine particles leads to an increase in coercivity of the recording medium, and this makes it difficult to perform data writing with existing magnetic heads.
To solve the foregoing problems, there has been proposed a technology so-called thermally-assisted magnetic recording. The technology uses a recording medium having high coercivity. When writing data, a write magnetic field and heat are simultaneously applied to the area of the recording medium where to write data, so that the area rises in temperature and drops in coercivity for data writing. The area where data is written subsequently falls in temperature and rises in coercivity to increase the thermal stability of magnetization. Hereinafter, a magnetic head for use in thermally-assisted magnetic recording will be referred to as a thermally-assisted magnetic recording head.
In thermally-assisted magnetic recording, near-field light is typically used as a means for applying heat to the recording medium. A known method for generating near-field light is to use a plasmon generator, which is a piece of metal that generates near-field light from plasmons excited by irradiation with laser light. The laser light to be used for generating the near-field light is typically guided through a waveguide, which is provided in the slider, to the plasmon generator disposed near a medium facing surface of the slider.
U.S. Patent Application Publication No. 2011/0170381 A1 discloses a technology in which the surface of the core of the waveguide and the surface of the plasmon generator (near-field light generating element) are arranged to face each other with a gap therebetween, so that evanescent light that occurs from the surface of the core based on the light propagating through the core is used to excite surface plasmons on the plasmon generator to generate near-field light based on the excited surface plasmons.
A thermally-assisted magnetic recording head that employs a plasmon generator as a source of generation of near-field light is configured so that the write head section includes the plasmon generator and a main pole that produces a write magnetic field. The plasmon generator and the main pole are located in close proximity to each other.
Part of the energy of the light propagating through the core is transformed into heat in the plasmon generator. This causes the following problems. During the operation of the thermally-assisted magnetic recording head, the temperature of the plasmon generator rises. The heat generated in the plasmon generator is transferred to the main pole disposed in the vicinity of the plasmon generator, thereby causing a rise in temperature of the main pole. This results in expansion of the plasmon generator and the main pole, so that part of the medium facing surface protrudes toward the recording medium. This causes an end of the read head section located in the medium facing surface to get farther from the recording medium, thereby causing the problem that a servo signal cannot be read during write operation. In addition, the rise in temperature of each of the plasmon generator and the main pole may cause corrosion of the plasmon generator and the main pole, and the rise in temperature of the main pole may degrade the magnetic properties of the main pole to cause deterioration of the characteristics of the write head section.
U.S. Patent Application Publication No. 2011/0170381 A1 discloses the following technology for suppressing a rise in temperature of the plasmon generator. Specifically, in the technology, conductive layers are provided on the lateral sides (opposite sides in the track width direction) of the main pole so as to be in contact with the plasmon generator. This publication describes that the conductive layers may be made of a nonmetallic material having a high thermal conductivity such as SiC. According to this technology, the heat generated in the plasmon generator is directly transferred to the conductive layers to enhance the heat dissipation performance of the plasmon generator so that a rise in temperature of the plasmon generator is suppressed. U.S. Patent Application Publication No. 2011/0170381 A1 further discloses employing SiC as the material of parts around the plasmon generator.
The technology disclosed in U.S. Patent Application Publication No. 2011/0170381 A1 makes it possible to suppress a rise in temperature of the plasmon generator. However, the problem with this technology is that heat is easily transferred from the plasmon generator to the main pole directly, so that it is difficult to protect the main pole from the heat generated by the plasmon generator.